Not applicable.
Not applicable.
Not applicable.
The present invention relates generally to cable terminals and cable assemblies such as may be used to connect to a battery post terminal.
Many types of cable terminals have been developed to connect to battery terminals. A common type of battery terminal on a car battery is a post terminal, which is basically shaped as a truncated cone and made of lead alloy. Typical cable terminals for attaching a cable to the battery post have a split, tapered hole that clamps onto the battery post when a clamping bolt is tightened. This can distort the tapered bole, reducing contact area between the cable terminal and the battery terminal, thus increasing series resistance. The clamping bolt is also typically a metal that is galvanically dissimilar from the metal of the cable terminal. This can result in corrosion, particularly in light of the proximity of battery acid and the availability of moisture in the environment.
However, such conventional cable terminals are easy to make and generally allow molding or casting the body of the terminal directly to the stripped end of a cable to make a cable assembly. Unfortunately, the cables are typically copper, while the cast terminal body is typically a lead alloy. This introduces another area of potential galvanic corrosion, particularly if the cable is loosened in the cable body as a result of stress or vibration, allowing moisture to infiltrate to the contact zone between the dissimilar metals.
Casting the cable into the cable terminal body typically results in a cable of fixed length and cable diameter. Repair shops and parts suppliers therefore typically have to carry many different cable assemblies to address the different applications and intended uses. After-market cable terminals are available with a bolt-tightened saddle clamp, but these saddle clamps are typically a galvanically dissimilar metal (galvanized steel) than the lead-based clamp body or cable strands (typically copper). Corrosion and poor electrical contact can result.
A locking ring-type battery connector was developed to avoid the disadvantages associated with the bolt-type cable terminal clamp. This connector uses a single type of metal for two pieces in a cam-type locking arrangement. Such a connector is generally described in U.S. Pat. No. 4,664,468 entitled BATTERY CONNECTOR by Woodworth, issued May 12, 1987. Unfortunately, this connector suffers from a number of problems. First, the rotating locking ring must be aligned with the fixed rings of the battery connector when being connected to the battery post. In other words, the locking ring is a separate part that may be dropped and lost when attaching or removing the battery connector from the battery.
Another problem arises in the attachment of the cable to the battery connector. As with the clamping bolt-type prior art connector, the body of the locking ring-type connector can be molded onto a cable. This can suffer from the same galvanic corrosion and cable loosening described above. The battery connector is also described as being connected to a cable using an expansion screw to force the strands of the cable against an inner surface of a cavity in the battery clamp. As with the clamping bolt, the expansion screw creates a source of galvanic corrosion and also creates another path for electrolyte incursion into the cavity containing the cable end. Even a lead-plated steel screw loses the plating and pinholes, allowing moisture to infiltrate to the cable end and exposing dissimilar metal, which will accelerate galvanic corrosion.
Therefore, a secure, corrosion resistant cable terminal suitable for attaching to post connectors is desirable. It is further desirable that the terminal be easy to manipulate when connecting or disconnecting the cable.
A cable terminal has a cable terminal body with a first ring portion and a second ring portion and a locking ring. The cable terminal body and locking ring are made of galvanically similar materials. In particular embodiments, the cable terminal body and the locking ring are cast from a lead alloy. In other embodiments, the cable terminal and locking ring are cast from other metal(s), such as brass, bronze, or aluminum, or are machined, or made using a combination and variety of methods. The locking ring operates as a cam lock to hold a terminal post against the fixed ring portions. A crimp tube extends from the cable terminal body and is configured to be crimped to a cable end of a preselected size that is stripped of insulation. At least the outer surface of the crimp tube is a metal that is galvanically compatible with the cable terminal body and locking ring material(s). In a particular embodiment, the crimp tube is a lead-plated copper tube that is cast into the cable terminal body, which is made from a castable lead-antimony or lead-calcium alloy, to form a sealed crimp socket. In a further embodiment, the stripped end of the cable is tinned with lead-based solder and the tinned cable strands cold weld to the lead-plated interior of the crimp tube during the crimping process.
In another embodiment, the corrosion-resistant cable terminal is joined to a cable by crimping. Only galvanically similar (compatible) metals are exposed, thus avoiding galvanic corrosion. A piece of heat-shrink tubing with heat-sensitive adhesive (sealant) is formed over the end of the crimp tube where the cable exits, thus sealing the crimp socket and cable end from moisture.